User blog comment:SpyTec/Purschase locations/@comment-12138097-20150419182151
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I agree for the most part. This game isn't like other MMOs where there are a few static vendors that sell a specific range of items - if that were the case then I could understand cataloging purchase locations. In E:D though it appears that sometimes stations will carry certain modules/ships and then (either a few days or a few patches) later they will change their stock thus making the purchase location lists outdated.
As you said an app or some sort of website that hooks into their api would be much better suited to displaying purchase locations.